Polycarbonate resins have hitherto been known as they have the best impact resistance and a good heat resistance, among engineering plastics. For that reason, they are used in various fields utilizing these features; however, they have defects such as a poor chemical resistance, a poor molding processability, and a thickness dependence on the impact resistance.
On the other hand, thermoplastic polyesters have a good chemical resistance and a good molding processability, but they have defects of a poor impact resistance and a poor dimensional stability.
With the aim of utilizing the features of each resin and covering the defects, various resin compositions have been proposed. For example, it has been attempted that the impact resistance, the heat resistance, the chemical resistance, the weatherability, and the moldability, which are required for automobile parts, are simultaneously satisfied.
A resin composition including a polycarbonate resin and a polyester modified with polyethylene glycol, polytetramethylene glycol, or the like, is also proposed. However, the composition has an improved moldability, but the heat resistance thereof is insufficient for exterior parts for automobiles.
A resin composition including a polycarbonate resin, and a polyester-polyether copolymer having block units of a polyalkylnene glycol adduct of a bisphenol and produced using a germanium catalyst, is also proposed. For example, Patent Document 1 discloses a resin composition including 30 parts of a polyethylene terephthalate block-copolymer having 30% of a polyethylene oxide adduct of bisphenol A having a molecular weight, of 1000 and 70 parts of polycarbonate, whose moldability, heat resistance and impact resistance are well-balanced without deteriorating its surface appearance of the molded article. The publication discloses that in this composition, the impact resistance is improved by admixing a graft-copolymer including an elastomer as an impact resistance improver.
At the present day, in electric appliances such as cell phones and personal computer housings and parts for vehicles such as fenders, door panels, and back door panels for automobiles, weight reduction is strongly desired, and accordingly it is advanced to reduce a wall thickness of a molded article. In order to response this requirement, a resin composition, which is a molding material for the molded article, is desired to have a further improved moldability and impact resistance.
Patent Document 1 discloses, as described above, that the resin composition having a good thin-wall moldability can be obtained by using the polyester-polyether copolymer, and the composition can provide products with a high quality in electric appliances such as cell phones and personal computer housings, and large-sized molded articles such as fenders, door panels, and back door panels for automobiles, which are required to have a reduced wall-thickness. However, in order to response the requirement to further reduce the weight, if the composition in Patent Document 1 is used for a large-sized molding which is required to have a further reduced wall thickness, the resulting fluidity is sometimes insufficient. In such a case, a measure is taken in which a molding temperature is set at a higher temperature to improve the fluidity. As a result, the resin is thermally deteriorated to generate decomposed gases, thus resulting in worsened appearance of the molding, with the impact resistance and the heat resistance being also decreased.